Focusing electrode with bent support arms to reduce high voltage arcing

ABSTRACT

A FOCUSING ELECTRODE FOR USE IN A CATHODE-RAY-TYPE KINESCOPE HAVING A PAIR OF OUTWARDLY EXTENDING ARMS ADAPTED FOR ENGAGEMENT WITH AN INCLUDED SUPPORT SECURING THAT ELECTRODE IN POSITION WITH RESPECT TO OTHER ELECTRON GUN ELEMENTS OF THE KINESCOPE, WITH THE OUTWARDLY EXTENDING ARMS HAVING FIRST AND SECOND BENT EXTREMITIES TO PROVIDE THE DESCRIBED ENGAGEMENT AND IN A MANNER PRESENTING AN OVERALL SURFACE AREA TENDING TO LESSEN THE POSSIBILITY OF ARCING WITHIN THE KINESCOPE.

United States Patent John McQueen Leonard D. Minutillo, Sayreville, NJ. 811,486

Mar. 28, 1969 June 28, I971 Griffiths Electronics Inc.

Linden, NJ.

Inventors Appl. No. Filed Patented Assignee FOCUSING ELECTRODE WITH BENT SUPPORT ARMS TO REDUCE HIGH VOLTAGE ARCING 3 Clalms,6 Drawing Figs.

u.s. Cl 313/85, 3 l 3/256, 3 1 3/262 m. Cl HOIj 19/38, H0] j 19/421101 j 29/46 Field of Search. 313/82, 70,

[56] References Cited UNITED STATES PATENTS 3,254,251 5/1966 Hughes 313/70 3,309,559 3/1967 Giacchetti et al 313/82 Primary ExaminerRoy Lake Assistant ExaminerV. Lafranchi Attorney-Ostrolenk, Faber, Gerb & Soffen ABSTRACT: A focusing electrode for use in a cathode-raytype kinescope having a pair of outwardly extending arms adapted for engagement with an included support securing that electrode in position with respect to other electron gun elements of the kinescope, with the outwardly extending arms having first and second bent extremities to provide the described engagement and in a manner presenting an overall surface area tending to lessen the possibility of arcing within the kinescope.

FOCUSING ELECTRODE WITH BENT SUPPORT ARMS TO REDUCE HIGH VOLTAGE ARCING This invention relates to cathode ray tubes, in general-for example, of the type designed to reproduce a television picture-and to electrostatic focusing electrodes used therein, in particular.

As is well known, focusing electrodes are employed in cathode ray tubes of the type described to focus the electron beam on the screen of the tube to develop an image. As is also well known, this electrode is positioned in the electron gun of the tube at a location beyond the first and second anodes which serve to speed up the electrons directed towards the screen and to collect any secondary electronsemitted by the fluorescent or phosphorescent coating of the screen when struck by the electron beam. These three electrodes, as well as the control grid and cathode of the electron gun assembly when included in a tricolor picture tube, are typically held in exact position by being secured to a multiformed glass or similar such member included within the envelope of the tube. In the tricolor kinescope, for example, three such members are included and serve to exactly position the electron beam produced by one of the three included electron guns, with respect to the beam produced by each of the other two guns.

In these electron gun assemblies, the accelerating potential applied to the second-anode closest to the focusing electrode is typically of the order of -25 kilovolts. In the Einzl arrangement, the focusing electrode is positioned midway between two such second anodes, each of which is maintained at this typical kilovolt potential. In all these arrangements, the potential applied to the focusing electrode is substantially less, with four hundred volts being a typical value.

Kinescopes presently in use also include a conductive coating on the inside of the envelope of the cathode ray picture tube. This coating, called aquadag, is electrically connected to the second anode and carries the same kilovolt potential as does the second anode. Furthermore, there is developed within the neck of the kinescope a charge distribution such that the same kilovolt potential exists along the neck of the tube. With these constructions, it therefore becomes possible for the electric field developed in the region of the focusing electrode to extend to that lower potential element and cause arcing with it at the point where the focusing electrode is secured to the multiformed glass or similar member, especially if the securement of the electrode to the member is by way of structure which is of small surface areafor example, where the securement is by way of a very thin element. As is well known, such arcing deleteriously effects the operation of the kinescope and severely distorts the image reproduced on the screen of the picture tube.

It is an object of the present invention, therefore, to provide a focusing electrode assembly in which the possibility of arc ing is substantially reduced.

It is another object of the present invention to provide such a focusing assembly for use where the difference in potential between that applied to the focusing electrode and the accelerating electrodes of the picture tube are of the order of tens of thousands of volts.

It is a further object of the invention to provide a focusing electrode which when held in place by a multiformed glass or similar such member presents a larger surface area to any electrostatic fields existent in the picture tube then has been presented by focusing electrodes previously employed in electron gun assemblies.

As will become clearer hereinafter, a focusing electrode constructed in accordance with the invention includes a cylindrical lens portion through which the electron beam produced by an electron gun passes and to which the focusing voltage is applied. The electrode also includes a pair of arms located at opposite sides of the cylindrical structure for insertion into the multiform glass or similar such member to be held in exact position with. respect to the other elements of an electron gun assembly and, also, with respect to corresponding elements of additional electron gun assemblies in a tricolor kinescope. Each of these focusing electrode arms includes first and second portions extending at substantially right angles to the surface of the arm for securement with the multiglass form. Besides serving to secure the focusing electrode to the stationary support, one of these right-angle portions serves to present a greater surface area to any electrostatic fields present in the envelope of the kinescope than is presented by previously employed structures. As will be appreciated, this increased surface area serves to minimize the possibility of arcing.

For a better understanding of the present invention together with further and additional objects thereof, reference will be had to the following description when taken in connection with the drawings, in which: FIG. 1 is a front view of a focusing electrode connected in accordance with the present invention;

FIG. 2 is a detail of the arm portion of the focusing electrode;

FIG. 3 is a cross-sectional view of the focusing electrode of FIG. 1 taken along the section lines B43 and rotated to a horizontal position; a

FIG. 4 is a detailed view of the curl portions of the sectional view of FIG. 3;

FIG. 5 is a cross-sectional view of the focusing electrode of FIG. 1 taken along the sectional lines A-A'; and

FIG. 6 is a side view of the arm portion of the focusing electrode of the present invention. 7

Referring now to FIG. 1, the front view of the focusing electrode there shown includes an annular ring or housing 10 having inside and outside surfaces 11 and 12, which together represent the inner and outer wall of the cylindrical lens portion of the focusing electrode. The focusing electrode also includes a pair of substantially identical support arms 13 and 14 which serve to position the focusing electrode in the electron gun assembly of a cathode-ray tube, particularly of the kinescope variety. Although not shown as such, it will be understood that electrons flowing from the electron gun of the kinescope flow into the plane of the paper (the axis of the housing) and are focused to a spot on the screen of the kinescope by a voltage of typically 400 volts applied in a manner not shown to the focusing electrode. The diameter of the inner section 11 of the annular ring 10 is approximately 0.35 inches while the diameter of the outer section 12 is approximately 0.46 inches, with the more precise values being indicated as shown in the view of FIG. 5.

It is to be understood that the view of FIG. 1 is one in which the support arms 13 and 14 have been bent so as to provide two portions thereof l5, l6 and 17, 18 that are bent at substantially right angles outward from the plane of the paper. As will subsequently become clear, these right-angle arm portions are employed to secure the focusing electrode to the multiform glass member serving to fixedly position the elements of the electron gun assembly within the cathode-ray kinescope.

FIG. 2 shows the detail of one of the support arms 13 of the focusing electrode assembly of FIG. 1, prior to the substantially right-angle bends. The support arm 13 includes a base portion 20 which, in the fabrication of the focusing electrode, is intended to be bent at a substantially right angle to the surface of the arm 13 and outward from the plane of the paper along the bend line 21 (i.e. in a plane parallel to the axis of the housing I0). The arm 13 also includes a top portion 22 which, in the fabrication of the focusing electrode, is intended to be bent outward from the plane of the paper along a second similar bend line 23, parallel to the axis of the housing. A vertical portion 24 serves to join these two surfaces and lies in a plane parallel to the plane of the paper. As indicated, the top portion 22 of the arm 13 prior to its bending along the line 24 is at an angle of l5 with respect to the base portion 20. In this manner, the two extremity portions 20, 22 form a substantially block C-structure with the arm 13, with the upper portion 22 of the block C being inclined downwards towards the lower portion 20.

FIG. 3 shows a sectional view of the focusing electrode of FIG. I along the lines 8-3 in the direction shown and rotated through an angle of 90 so as to appear in a left-to-right configuration in the drawing. The cylindrical nature of the focusing electrode is shown in this view, as is the fact that its horizontal dimension is greater than its vertical dimension. Also shown is the fact that the outer portion 12 is of a dimension greater than the inner portion II. In other words, the form of the focusing electrode is that of a right-angle cylinder sandwiched between upper and lower plate portions of greater dimension.

FIG. 41 shows the curl sections 25 of FIG. 3 in greater detail. The dimensions of this curl are also shown.

FIG. 0s the drawings shows a sectional view of the focusing electrode of FIG. I along the lines indicated by A-A' and with the top portion 22 of the arm 13 being in position prior to its substantially right-angle bend. The notation 26 represents the outline view of the base portion of the arm 113 when bent to be in its right-angle relationship with respect to that arm.

FIG. 6 shows the view of the focusing electrode of FIG. I taken along the section lines C-C in the direction shown. The arm M is here shown with the base portion 118 in the position it would be in prior to its being bent along the bend line 21 of FIG. 2.

In the usage of the focusing assembly illustrated by FIGS. 1- 6, it will be understood that the two portions 20, 22 of the arm of FIG. 2 are to be inserted in the multiform glass member while that structure is still in its molten state. These structures 20, 22 though initially in the plane of the surface of the arm will be bent downwards and away from that surface when the multiform glass member is compressed against the elements of the electron gun assembly to position those elements in fixed relationship. The resulting compressive force is such as to secure the focusing electrode to the glass member unit in a manner to present a substantially greater surface area to any high voltage electrostatic fields presents in its vicinity than would be presented by a surface area connecting the focus electrode to the multiglass form structure in a plane substantially perpendicular to that of the cylindrical electrode and to the stationary glass form member itself.

Such an assembly has been found to resist arcing of high voltages present in the vicinity of the focusing electrode in a much greater manner than with the prior horizontal-type connection just described. With this arrangement, as illustrated in the drawings, arcing and the problems it causes is much less prevalant. Whilethe prior-type connections may have sufficed for focus assembly insertions in monochrome picture tubes, they have been found to be less efficient when used in tricolor kinescopes. The reasons for this discrepancy has been found to result from the fact that the differences between the second and anode voltages in blaclc-and-white picture tubes is of the order of ltilovolts or so while in tricolor picture tubes the difference in potential is approximately 26 kilovolts. It has been found in picture tube manufacture that arcing and corona problems are more severe once its anode voltages exceed 20 kilovolts.

However, while the focusing electrode and the manner of its securement to the supporting member is particularly attractive in the tricolor kinescope where the voltages are substantially higher, it will be apparent that its use in the monochrome picture tube will also prove advantageous. As compared to the type of focusing electrode previously employed in such an environment, it will be appreciated that the manner of securing the focusing electrode to the support structure for the picture tube is such as to present a greater surface area, which not only reduces the possibility of arching, but also tends to further strengthen the bond between the focus electrode and the support structure itself.

It will also be noted that in present day technologies, where the cost of the picture tube in color television receivers represents the most significant cost element in its manufacture, the use of a focusing electrode of the type herein described, while of almost insignificant cost either in material or in fabrication time, will be effective to minimize arcing and to protect that tube. Thus, the major component on the receiver can be protected by expending an amount of money and fabrication time which is inconsequential.

We claim:

l. A focusing electrode for use in an electron gun assembly also having an electron emitting cathode, a control grid, first and second anodes and support means for fixedly securing said elements in a spaced, cooperating arrangement in a cathode-ray-type kinescope having a viewing screen comprising:

a substantially cylindrical housing having a pair of open end portions and a central axis along which electrons from said cathode flow to energize the screen of said lcinescope;

a pair of support arms extending outwardly from said housing and integral with at least a portion thereof for engagement with said support means to secure said focusing electrode so as to concentrically align said open end portions with said control grid and said first and second anode elements;

said support arms lying in a plane substantially perpendicular to said axis of said cylindrical housing and having first and second extremities thereof bent towards the axis of said housing and engaging said support means;

whereby the surface area presented by said support arms in a plane perpendicular to said housing axis is of an amount to lessen the possibility of arcing to said focusing electrode by any high potential electrostatic field existent within said kinescope.

2. A focusing electrode as defined in claim I wherein said first and second extremities of said support arms, form a substantially block C-structure with said support arms, with the upper portion of the block C-structure being inclined downwards towards the lower portion of the structure.

3. A focusing electrode as defined in claim I wherein saNd first and second extremities of said support arms are bent in a direction to each lie in a plane parallel to the axis of said cylindrical housing. 

